Revert of Make TestRenderWidgetHostView::Show/Hide call through to RWHI (patchset #9 id:160001 of https://codereview.chromium.org/1713473002/ )

Reason for revert:
Speculative revert. Many tests are crashing on CrOS, yours is the only plausible CL. Apologizes in advance if it turns out to be the wrong CL.

Example failure:
https://uberchromegw.corp.google.com/i/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/22356

Original issue's description:
> Make TestRenderWidgetHostView::Show/Hide call through to RWHI
>
> Before this patch, after calling test_web_contents->WasHidden() on a
> TestWebContents, test_web_contents->GetMainFrame()->GetVisibilityState()
> would still return blink::WebPageVisibilityStateVisible, because
> TestRenderWidgetHostView::Hide didn't propagate the WasHidden to
> RenderWidgetHostImpl (unlike all the non-test implementations of
> RenderWidgetHostView).
>
> This patch fixes that. There don't seem to be significant downsides to
> propagating the WasHidden to RWHI; it tries to send a few IPC messages,
> but since Send is stubbed out, those are simply discarded.
>
> I did have to add a null check in
> RenderWidgetHostViewBase::GetPhysicalBackingSize (called from
> RWHI::GetResizeParams, called from RWHI::WasResized, called from
> RWHI::WasShown), since gfx::Screen::GetScreen() sometimes returns null
> in unit tests.
>
> And I had to update some of the web_contents_impl_unittest.cc tests,
> which were expecting interstitials etc to be hidden, even though RWHI
> generally defaults to visible (it would be possible to instead keep the
> is_showing_ bool in TestRenderWidgetHostView, but it seems weird to
> allow TRWHV and RWHI to disagree about whether they are visible.
>
> Also there's one test that manages to hit a null screen on navigation,
> so I added a TestScreen to
> ExtensionContextMenuModelTest.TestPageAccessSubmenu.
>
> BUG=577336,636953
>
> Review-Url: https://codereview.chromium.org/1713473002
> Cr-Commit-Position: refs/heads/master@{#449606}
> Committed: https://chromium.googlesource.com/chromium/src/+/1c496374204313ae4233bc19c6495c8c2b0ee660

TBR=sievers@chromium.org,boliu@chromium.org,sky@chromium.org,johnme@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=577336,636953

Review-Url: https://codereview.chromium.org/2684993011
Cr-Commit-Position: refs/heads/master@{#449797}